Writing instrument



FIG. 1 is a side perspective view of a writing instrument, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a right elevational view thereof; the left side being a mirror image thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a top plan view thereof. 

The ornamental design for a writing instrument, as shown and described. 